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Lawn-Boy began manufacturing its brand of power mowers in the early 1950s. Since that time, the machines have touted engines made by Lawn-Boy, Briggs & Stratton and other manufacturers. Early Lawn-Boy engines were equipped with a coil; in later years, solid state ignition technology replaced the coil with electronic components. This new system also required a clearance or air gap to be set so the engine starts properly. Lawn-boy recommends using the Lawn-Boy air gap gauge to set clearance gaps at 0.010 inch. The part number for the gauge is 604659. If you don’t have this gauge, you can use a feeler gauge of this thickness made by any manufacturer.

D-400 Series Engines With Coils

Lawn-Boy D-400 series engines are two-cycle engines with a “twin spark” ignition system. The first spark starts the engine, and a second spark keeps the engine running. The D-400 engines are equipped with an ignition coil. Lawn-Boy recommends setting the clearance, also called the air gap, between the coil and flywheel at 0.010 inch. Lawn-Boy 7260 series mower models, made in the 1970s and 1980s, are equipped with Lawn-Boy brand engines in the D-400 series, specifically the D408 and D409.

D-600 Series Engines Without Coils

In 1972 Lawn-Boy began manufacturing coil-less, solid-state ignition systems on its D-600 series engines. On these engines the air gap is set between the flywheel and the capacitor discharge module at 0.010 inch. Lawn-Boy models 5270 and 5271 are both equipped with Lawn-Boy brand D600 engines. Models 5272 through 5275 have the D601 engine. These engines were made from 1972 to 1978.

F-Series Engines Without Coils

In 1977 Lawn-Boy began producing its F-series of two-cycle engines. It contains 21 fewer parts than previous engines, and the manufacturer claims it produces more power than the 400 series or 600 series. The F-series of engines use the solid-state ignition system. The clearance setting is 0.010 inch between the flywheel and capacitor discharge module. Lawn-Boy models in the 0292 series, made in 1980 to 1982, have F210 and F211 engines. Models in the 0392 series, made from 1980 to 1982, are equipped with F250 and F251 engines.

Briggs & Stratton Engines

If your Lawn-Boy mower has a Briggs & Stratton engine, the clearance needs to be set according to the air gap Briggs & Stratton recommends. Common settings are between 0.006 to 0.010 and 0.010 to 0.014 inch. The precise setting is listed in the owner’s manual that came with the engine. The clearance setting for Briggs & Stratton 110000 series engines, found on Lawn-Boy models 397 and 427, is 0.006 to 0.010. For engines in the 130000 and 190000 series, on the Lawn-Boy models 2650 and 2580 respectively, the clearance setting is 0.010 to 0.014.

About the Author

Diana K. Williams is a certified Master Gardener, has more than a decade of experience as an environmental scientist, and holds a Bachelor of Science degree in biology and environmental studies from the Ohio Northern University. Williams is a winner of Writer’s Digest Magazine's annual writing competition.